what do i do? fast!

my leaves were droopy this morning with browning and twisting so i turned off water and lights cleaned res.
lights 18-6
ph 5.5
temp 68-78 i have pics help fast

it drives me mad when noobs ask for help but give us no info ...

what lights u using ? u soil or hydro ?humidity ? are u feeding yet ? how often u water ? how old is the plant and post the pic up u said u have

im running a t5 424 wat light, my hum. sits between 38percent and 45 my roommate put a bunch of nut in the water and they started to nut burn so i pulled the res and cleaned and just replaced it with distilled water it waters 15 min ever 3 hours while the lights are on the cycle is 18-6 the pics were yesterday afternoon ill post some new ones.